The invention relates to a laminated core of a stator of an electric motor and a method of producing it.
Laminated iron cores serve for guiding the magnetic field.
German Utility Model 18 82 073 discloses a laminated actuating magnet, having sheet-metal laminates provided on one side with preferably circular indentations in such a way that protrusions are formed on its opposite side and the sheet-metal laminates can be fitted together by interengagement of their indentations and protrusions to form a laminated core for the actuating magnet.
It is difficult in this way to achieve an optimum alignment of the sheet-metal laminates for providing an acceptable mutual angular positioning, without impairing the magnetic properties and consequently the operating behavior of the electric motor. Furthermore, this causes problems when fitting the windings.
On this basis, it is an object of the invention to provide a structural configuration of a laminated core for a stator of an electric motor, by which the production can be simplified and reduced in cost and which at the same time achieves the magnetic properties of comparable electric motors.
This object is achieved by an electric motor which has the following features:
a) at least one laminated core of a stator formed by stacked sheet-metal laminates,
b) sheet-metal laminates comprising mechanical individual poles and poles which are connected in the circumferential direction of the stator, with at least one pole shank and at least one pole shoe facing a rotor,
c) indentations of the sheet-metal laminates in such a way that the opposite sides of the sheet-metal laminates have protrusions and, as a result, the sheet-metal laminates form the laminated core of the stator by interengagement of their indentations and protrusions,
d) windings of the magnetic poles of the laminated core of the stator,
e) webs between the poles which connect the connected mechanical poles in the circumferential direction,
f) the axial set-up of the sheet-metal laminates of the laminated core of the stator has a predeterminable alternating succession of poles with a connecting web and poles without a connecting web.
An electric motor of this type is produced by the following method:
a) production of the mechanical individual poles and/or the poles connected in the circumferential direction by stamping in a progressive die,
b) the sheet-metal laminates formed by stamping are assembled in a predeterminable sequence,
c) the pole shanks protruding essentially radially outward and/or inward are provided with pre-wound coils,
d) the entire laminated core of the stator is encapsulated and/or impregnated.
The laminated core according to the invention of a stator of an electric motor can be produced by a small number of simple method steps. Thus, this method can easily be automated. As a consequence of its optimized constructional design in comparison with conventional electric motors, the laminated core of the stator has comparable electromagnetic properties, so that no power losses of the electric motor are experienced. The laminated core of the stator, assembled in a predetermined sequence of the sheet-metal laminates, if need be with the assistance of a mounting mandrel, has pole shanks protruding inward (toward the air gap) or outward; this depends on whether the sheet-metal laminates of the connected poles are connected to one another at their outer circumference or their pole shoes.
These pole shanks are accordingly preferably provided with windings from the inside or outside. In this respect, windings of all forms, interconnections and types, such as for example a double-layer fractional-slot winding, can be used. The construction of the laminated core of the stator allows pole shoes preferably turned into tooth-wound coils to be fitted onto the pole shanks of the laminated core. In this arrangement, the tooth-wound coils can be positioned in virtually any way desired in the circumferential direction on the pole shanks to obtain desired motor properties, such as for example reduced torque ripple.
The fixing of the windings preferably takes place by encapsulating and impregnating the laminated core. In this way, not only the mechanical fixing and compacting of the laminated core is achieved but also an electrical insulation of the windings from one another. Similarly, as an alternative or additional measure, mechanical fixings of the windings, for example in the form of slot wedges and/or pole shoes, can be used in the case of the pole shanks provided with coils from the inside.
For magnetic reasons, including to minimize the stray flux, only some of the sheet-metal laminates have a magnetically conducting connection of the pole shoes. On the other hand, some of the sheet-metal laminates having pole shoes which are not magnetically connected, include such an optimized slot opening between the pole shoes as to avoid virtually any saturation effects of the poles. The slanting of the axially running slots of the laminated core of the stator further brings about a reduction in the slot engaging moments. Furthermore, the additional mechanical and magnetic loads of the individual poles during the operation of the motor can be permanently fixed in their position by the connecting webs between the poles of a sheet-metal laminate of this type.
The number of indentations per sheet-metal laminate allows an optimum alignment of the overall laminated core to be achieved along with mutual angular positioning of the individual sheet-metal laminates. There are in this case preferably two indentations, since further indentations are statically excessive and counterproductive to an optimum alignment and mutual angular positioning of the sheet-metal laminates.
No reworking of the stator bore is necessary as a result of the modular construction of the laminated core. This dispenses with the need for a machining step which, in the form of a metal-cutting operation, entails the risk of producing metal chips in the laminated core. To remove such metal chips from the laminated core is also complicated and time-consuming, so that there is always the risk of the operation of the electric motor being adversely affected.
In a further embodiment, the sheet-metal laminates of a first layer of the laminated core of a stator have no indentations, and the sheet-metal laminates of a final layer of the laminated core of the stator have no protrusions, so that no design constraints are necessary, for example when attaching a fan or a brake in this area, to realize optimum properties of the electric motor in a compact construction.
In a further preferred embodiment, the laminated core is fitted into a magnetic yoke. Hereby, all positive, non-positive and material-interconnecting types of connection or combinations thereof are possible. If the sheet-metal laminate of the connected poles has the connection of these poles on the outer circumference, motors without housings can also be preferably realized in this way. Cooling devices for the operation of the electric motor are provided both in the magnetic yoke and for the sheet-metal laminates themselves. These devices are preferably cooling channels and/or measures for enlarging the surface area of the laminated core.
In a further embodiment, the laminated cores are subdivided into axial cores and/or cores resembling segments of a circle. This simplifies the production specifically of large electric motors.